Epoxy resins and phenolic-hydroxyl containing resins are used as materials such as adhesives, molding materials, and paints. These resins are also widely used in electrical and electronics engineering as materials such as semiconductor sealants and insulators for printed circuit boards because of their properties such as high heat resistance and moisture resistance after curing.
Among such various applications, technical advances are being made in the field of semiconductor sealants, including the shift to surface-mount packages such as BGAs and CSPs, the support for lead-free solders, and the elimination of halogenated flame retardants. Specifically, there is a need for a halogen-free resin material with a higher heat resistance, a lower thermal elastic modulus, and a higher flame retardancy. Along with these properties, resin materials, to which fillers such as silica are added for use as semiconductor sealants, require low viscosity and high flowability to achieve a higher filler content. With the increasing signal speed and frequency in various electronic devices, a correspondingly lower dielectric constant has also been required.
There are known resin materials designed to meet such various requirements, including a benzylated phenol novolac resin prepared by reacting a phenol novolac resin with p-methylbenzyl methyl ether at 140° C. for 5 hours and an epoxy resin prepared by reacting the benzylated phenol novolac resins with epichlorohydrin (see PTL 1).